What the Heck is this Hose ?

Hi does anyone know what this hose is?
It was cracked at the adapter and failed smog, luckily I was able to cut it short with a razor and attach it back on along with a hose clamp to pass smog test. But what is it? My original thought was PCV hose but other threads I read showed PCV valve elsewhere.. Ideas?

photos taken from driver side over the engine bay. Hose connects into the unit in the fourth photo.

 

Anyone ?

 

Does it go from valve cover to intake? Can’t really tell on my phone, probably crank case ventilation

 

i can definitely agree with you it is not pcv valve hose that is elsewhere!

 

Not from valve cover but it does go to intake. It’s in the rear of the motor.. pictures really aren’t that great. My guess is some type of ventilation though

 

Looks like some kind of crank case ventilation hose.

Mine runs behind the top of the engine, not around the front.

 

This is more likely, which I’m guessing is separate from the pcv valve hose

I only ask because this hose was damaged, wondering if the cause of damage is a compromised pcv valve or something else. Or maybe just an old hose.

 

Rubber hoses have a limited shelf life, that’s all, it’s normal

 

Looks like the Idle Air Control line, but I am not 100% sure.

 

Crank case ventilation hose. Normally its just a pressure fit but over the years it can loosen off, so someone added a hose clamp to ensure it stays on.

 

I added the hose clamp, before it looked like this

Wondering if I should replace the pcv valve too but sounds like it’s a different hose system

 

Hmm u might actually be right

 

Pcv = positive crank case ventilation

 

Yes but this hose doesn’t go to the positive crank valve, so this hose is something else. Which is why I made this thread

 

Then idk, I have a 4.0

 

I think it’s the IAC line

 

It's part of the PCV system.
Specifically, the "filtered fresh air source" for the system. The ventilation flow goes from the intake tube to the driver side rear valve cover, thru the engine and out the pass side valve cover at the PCV valve to enter the intake just downstream of the throttle plate. This ventilating air is drawn by engine vacuum, regulated somewhat by the PCV valve to prevent a full on vacuum leak.

Earlier 3.4's have a smaller connector (no box) at the intake tube, like below.
Blue is fresh air, red is the same air that has picked up or "ventilated" crankcase vapors along the way.

 

Hi thanks, this is helpful

I'm wondering, if ventilation from intake tube to driver side valve cover is cracked or compromised (blue arrows) what will be the outcome?
Motor will pull in unfiltered air? A rough idol? Uncontrolled emission? Lean fuel mixture?

Why not just bypass this whole system completely lol seems like recycling emissions would be terrible for the motor and give poor power

 

A leak in the blue line will introduce unfiltered air into the engine. It could also allow a back flow of air (under certain throttle/load conditions) into the intake tube downstream of the mass airflow sensor, causing the reported MAF value to be skewed. All this is going to be relative to just how bad the leak is. A simply cracked hose might go unnoticed.

PCV systems started to appear in earnest around 1962ish. They were the first and most simple pollution control and typically work very well. Before crankcases were ventilated, sludgy condensates would simply collect in the engine. The crankcase vapors or blow-by was just allowed to "waft" out of the engine typically from an opening provided to relieve any pressure build up.

The continuous or positive ventilation has very little detrimental effect on anything less than race engines, providing the system is working/engineered correctly. The 3.4 PCV system works pretty well. The 2ng gen 4.0 is another story. That system tends to carry a fair bit of engine oil mist along with the flow. Many 4.0 folks install a "catch can" to condense and capture this oil before it gets burnt.

 

Hmmm
So when pcv valve is closed or compromised it shuts the system down so the motor builds up pressure and can blow seals, leak oil etc

Yea seems like a completely redundant system to have (other than being good for the environment) but super important if it fails can cause big problems over time

I wonder if keeping the red hose (pcv valve hoseline, red arrows) unattached will best for the motor. Or if it’ll give codes or check engine if it’s disconnected